mmg_233_2013_genetics_genomicswikiaorg-20200214-history
Cucumber (Cucumis sativus L)
Genetically modified organisms (GMO) are organisms that have been genetically altered for scientific study or for the production of goods. A wide variety of organisms have been modified including bacteria, planets, and animals. One example of a planet that has been genetically modified is the cucumber (Cucumis sativus L). The cucumber is one of the most produced vegetables in the world, with approximately 57 million tons produced in 2011 (1). Cucumbers, however, are susceptible to a variety of infections from numerous pathogens including fungi, nematodes, bacteria, and viruses. Conventional breeding methods are inadequate to improve resistance to infections as there is little genetic variability amongst cucumbers (2). A common way of preventing soil born infections is to graft cucumbers onto the rootstocks of other cucurbitaceous family members (3). However this is a very time intensive procedure. Due to its importance and the inability to use traditional methods to impart resistance to infections, attempts have been made to genetically modify the cucumber. Method of Genetic Modification Cucumbers were first genetically modified in 1986 when the gene encoding neomycin phosphotransferase II, an enzyme that confers resistance to kanamycin, was transferred from Agrobacterium (4). Upon infection by Agrobacterium, transfer of plasmid DNA from the bacteria to plant cells occurs. DNA from th e plasmid is then incorporated into the genome of the plant cell (Figure 1). This results in the formation of a tumor-like growth. Thus the plasmid is referred to as the tumor inducing (Ti) plasmid and the DNA that is transferred from the plasmid is referred to as tumor DNA (T-DNA) (5). By changing the genes that are carried by the Ti-plasmid, an effective method for delivering genes has been developed. Ti-plasmids can be modified to carry genes that could impart resistance to infection or improve growth in what would normally be a non-optimal environment. In laboratory settings, Agrobacterium is generally co-cultured with plant cells. This facilitates gene transfer. The recombinant plant cells are then grown to full plants . Genetic Modifications of the Cucumber Agrobacterium has been used to transfer genes encoding cucumber mosaic virus (CMV) coat proteins. Transfer of these genes resulted in an increase in resistance to infection by CMV (6). Another study showed that transfer of a gene encoding for rice chitinase resulted in an increase in resistance to infection by gray mold (Botrytis cin erea) as well as the complete arrest of the molds propagation between cucumbers (7). However there have been few reported successes of the production of transgenic cucumbers. This is most likely do to difficulties in the transformation process (8). A recent study showed that alteration of the culture conditions in which Agrobacterium and cucumbers are grown can increase the success rate of transformation (8) (Figure 2). This is an important development as the cucumber is a very important crop which is susceptible to a wide range of infections. The ability to convey resistance to various pathogens would greatly enhance the cultivation of this important vegetable. Sources 1. http://faostat.fao.org 2. Plader W, Burza W, Malepszy S. Cucumber. In: Pua EC, Davey MR, editors. Biotechnology in Agriculture and Forestry 59. Transgenic Crops IV. Berlin: Springer; 2007. pp. 181–199. 3. Oda M. Use of grafted seedlings for vegetable production in Japan. Acta Hort. 2008;770:15–20. 4. Trulson AJ, Simpson RB, Shahin EA. Transformation of cucumber (Cucumis sativus. L) plants with Agrobacterium Rhizogenes. Theor Appl Genet. 1986;73:11–15. 5. Chilton MD, Drummond MH, Merio DJ, Sciaky D, Montoya AL, Gordon MP, Nester EW., Stable incorporation of plasmid DNA into higher plant cells: the molecular basis of crown gall tumorigenesis, Cell. 1977 Jun;11(2):263-71. 6.Nishibayashi S, Hayakawa T, Nakajima T, Suzuki M, Kaneko H. CMV protection in transgenic cucumber plants with an introduced CMV-O cp gene. Theor Appl Genet. 1996;93:672–678. 7. Tabei Y, Kitade S, Nishizawa Y, Kikuchi N, Kayano T, Hibi T, Akutsu K. Transgenic cucumber plants harboring a rice chitinase gene exhibit enhanced resistance to gray mold (Botrytis cinerea) Plant Cell Rep. 1998;17:159–164. 8. Nanasato Y, Konagaya K, Okuzaki A, Tsuda M, Tabei Y. Improvement of Agrobacterium-mediated transformation of cucumber (Cucumis sativus L.) by combination of vacuum infiltration and co-cultivation on filter paper wicks. Plant Biotechol Rep. 2013; 7: 267-276.